<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .box{
            width:100px;
            height:100px;
           background-color: rgb(49, 46, 46);
            margin: 100px auto;
            display: flex;
            justify-content:center;
        }
        .one{
            width:20px;
            height:20px;
            background-color: red;
            border-radius: 50%;
            align-self: center;
        }
    </style>
</head>
<body>
   <div class="box">
       <div class="one"></div>
   </div> 
</body>
</html>